Wide belt sanding machine with improved work feeding means

ABSTRACT

A wide belt sanding machine with a vertically oriented sanding head and an endless horizontally oriented conveyor belt having its top stretch sliding across a platen which is urged upwardly to press work on the conveyor belt into engagement with the sanding head, by &#39;&#39;&#39;&#39;air springs&#39;&#39;&#39;&#39; reacting between the platen and a conveyor frame in which the conveyor belt is mounted, with either high force for abrasive dimensioning of the work or with low force for finish sanding, the air springs being connectable with a pressure source through either of two pressure regulators, one set to hold the platen rigid up to the capacity of the machine but to yield if necessary to prevent an overload, and the other set to urge the platen towards the sanding head with a yielding force sufficient only for finish sanding.

Kiser et al.

[ Sept. 3, 1974 WIDE BELT SANDING MACHINE WITH IMPROVED WORK FEEDING MEANS [75] Inventors: Fred W, Kiser, Hopkins; Allan J.

Stinn,.South St. Louis Park, both of Minn.

[73] Assignee: Timesavers, Inc., Minneapolis,

Minn.

[22] Filed: Sept. 17, 1973 [21] Appl. No.: 397,837

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 226,272, June 26,

1972, abandoned.

[52] US. Cl. 51/138 [51] Int. Cl B24b 21/04 [58] Field of Search 51/135 R, 138, 61, 76

[56] References Cited UNITED STATES PATENTS 3,271,909 9/1966 Rutt et a1 51/138 X 3,394,501 7/1968 Carlson et al 51/138 3,608,245 9/1971 Fair, Jr. et al. 51/135 R FOREIGN PATENTS OR APPLICATIONS 230,761 12/1963 Austria 5l/l38 Primary Examiner-Othell M. Simpson [5 7 ABSTRACT A wide belt sanding machine with a vertically oriented sanding head and an endless horizontally oriented conveyor belt having its top stretch sliding across a platen which is urged upwardly to press work on the conveyor belt into engagement with the sanding head, by air springs" reacting between the platen and a conveyor frame in which the conveyor belt is mounted, with either high force for abrasive dimensioning of the work or with low force for finish sanding, the air springs being connectable with a pressure source through either of two pressure regulators, one set to hold the platen rigid up to the capacity of the machine but to yield if necessary to prevent an overload, and the other set to urge the platen towards the sanding head with a yielding force sufficient only for finish sanding.

6 Claims, 7 Drawing Figures PAIENTEDSEP3' m4 SIEU 1 N 4 FIGJ.

memmstrs I914 3.882.807

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HIGH LOW PRESSUQE fig PPESSUQE f5! REGULATOR IQEGULATOR WIDE BELT SANDING MACHINE WITI-I IMPROVED WORK FEEDING MEANS This application is a continuation-in-part of our copending application Ser. No. 266,272, filed June 26, I972 now abandoned.

This invention relates to wide belt sanding machines and has as its purpose to provide an improved feed bed system by which the work is carried through the machine. In a very general way, the sanding machine of this invention is similarto that of the Pendergast U.S. Pat. No. 2,876,600. In such sanding machines, there are one or more sanding heads each having an endless abrasive belt trained over rollers or drums, one of which is power driven to impart high speed orbital motion to the abrasive belt. The machine herein disclosed has two sanding heads, disposed vertically with their abrasive belt arranged to contact the top surface of the work fed through the machine.

The work is fed through the machine by a feed system or conveyor assembly that comprises an endless horizontally oriented conveyor belt, the top stretch of which coacts with hold-down rolls to grip the work and feed it through the machine with its top surface in contact with the abrasive belts. To adapt the machine to different work thicknesses, the conveyor assembly is adjustable up and down towards and from the sanding heads which are solidly supported against the thrust of the work thereon.

Obviously, the top stretch of the conveyor belt must be supported for it to coact with the hold-down rolls which press the work down onto the belt. For this purpose a platen or bed is mounted inthe conveyor assembly with its smooth flat top surface bearing against the underside of the top stretch of the belt.

Since the machine of this invention is intended to perform two quite different and incompatible results or operations namely, dimensioning of lumber, panels and a wide variety of workpieces, as well as finish sanding of plywood panels, door surfaces and the like the bed or platen must be capable of being held in a rigid position for work dimensioning and in a floating or yieldable manner for finishsanding. In recognition of these diverse requirements, it is an object of this invention to provide a bed or platen support which can be quickly adjusted to rigidly hold the same at a predetermined elevation from which it will not yield as long as the machine is not overloaded, or in a manner holding the work against the abrasive belts with a yielding force no greater than that needed for good finish sanding.

Another object of the invention is to provide for the adjustment of the force with which descent of the bed 'or platen is resisted.

Whether the machine is used to abrasively dimension stock or for finish sanding, it is important that the bed or platen remain truly horizontal at all times. To that end, it is' another object of the invention to so mount the bed or platen in the conveyor assembly that throughout its range of up and down motion with'respect to the structure of the assembly to which it is connected, the bed or platen is secure against tilting.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the invention, it being understood that changes may be made in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawings'illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a perspective view of a sanding machine embodying this invention, illustrating the in-feed end of its conveyor;

FIG. 2 is an in-feed end view of the machine with parts broken away and in section;

FIG. 3 is a top plan view of the conveyor assembly detached from the machine, with parts of its bed or platen broken away;

FIG. 4 is a side view of the conveyor assembly with parts broken away and in section;

FIG. 5 is a fragmentary perspective view, partially in section, of one of the four connections between the floating bed or platen and the structure of the conveyor assembly in which it is mounted;

FIG. 6 is a detail sectional view through FIG. 3 on the plane of the line 6-6; and

FIG. 7 is a diagrammatic illustration of the air pressure system employed to support the bed or platen either rigidly or floatingly.

Referring to the drawings, in which like numerals refer to like parts throughout the several views, the numeral 7 designates generally the main frame of a wide belt sanding machine embodying this invention, in the upper portion of which there are two conventional sanding heads 8 and, below them, a feed bed system or assembly 9 that is significantly difierent from prior work supporting and feeding structures.

The main frame which is preferably a weldment has a base section 10 with side sections 11 and 12 rising therefrom at opposite sides of the machine, the former being taller than the latter. Rigidly fixed to the top of the taller side section 11 and extending cantilever fashion therefrom towards the other side of the machine, are two horizontal arms 13, which in the industry are known as center bars. It is the center bars that carry the sanding heads 8. a

The sanding heads, as stated, are conventional. They comprise endless abrasive belts 14 trained over lower drums 15 and upper idler rolls 16. As shown in FIG. 1, the sanding head nearest the infeed end of the machine, hasa single lower drum 15 while the other head has a pair of parallel lower drums between which it is customary to locate a conventional pressure shoe not shown. Hence the abrasive belt of the first sanding head is supported against the thrust of the work directly by its lower drum 15, whereas the abrasive belt of the second head is held against the work by the conventional pressure shoe located between its pair of lower drums 15. The shafts of the lower drums are journalled in bearings mounted in the side frame 11 and in brackets 17 that depend from the underside of the free end portions of the center bars 13. The axes of these drums are thus fixed with respect to the center bars.

The upper idler rolls 16 are freely rotatably supported between the arms of yokes 18 which are supported on the center bars by the rams of air cylinders 19 that are fixed to the center bars. By means of these air cylinders, the idler rolls 16 can be raised as needed to tension the abrasive belts, and can be lowered to permit their removal and replacement.

Since the abrasive belts of the sanding heads engage the workpiece being acted upon with considerable force, and since exact parallelism is necessary between the undersides of the abrasive belts and the feed bed system or assembly 9, it is evident that during operation of the machine the center bars with the sanding heads thereon must be supported against any possible deflection but that support must accommodate removal and replacement of the abrasive belts. Accordingly, the outboard end of each center bar is rigidly but separably connected with the side frame section 12 in the manner disclosed in the copending application, Ser. No. 240,683, which is assigned to the assignee of the instant invention, and which is here merely indicated in FIG. 2 at 20.

The endless abrasive belts are orbitally driven in the conventional way by electric motors, one of which is identified by the numeral 21 in FIG. 2, where it is shown drivingly connected with the lower drum of the first sanding head.

The feed bed system or assembly'9 in accordance with this invention, comprises a rigid rectangular conveyor frame 22 and a bed or platen 23 mounted in this frame for limited up and down'motion relative to the frame.

An endless conveyor belt 24 trained over rollers 25 and 26 at the in-feed and out-feed ends of the conveyor assembly the latter of which is suitably driven coacts with spring pressed hold-down rolls (not shown) mounted in the main frame of the machine above the conveyor belt, to carry the work through the machine. It is of course the top stretch of the conveyor belt upon which the work is placed and by which it is carried into the machine and under the hold-down rolls; and to support this stretch of the belt against the thrust of the hold-down rolls and also provide the needed feed force between the work and the contact drum-supported abrasive belts, the top stretch of the conveyor belt slides across the smooth flat top surface of the bed or platen 23.

The entire conveyor assembly is supported for vertical adjustment on four jack screws 27, one depending from each of the four corners of the frame 22. The nuts 28 in which these jack screws are threaded are freely rotatably (but not longitudinally movably) mounted in the base section of the main frame, so that upon simultaneous rotation of the nuts the frame and all structure thereon may be raised or lowered as needed to adjust the machine to different work thicknesses. Such simultaneousrotation of the nuts 28 is effected by turning a hand wheel 29 which is drivingly connected with the nuts through a conventional transmission, part of which is indicated at 30 in FIG. 2.

Since all four jack screws rotate simultaneously and at the same rate during adjustment of the elevation of the conveyor assembly, the conveyor frame 22 rises and falls with a translatorymotion and, to guide that motion, lugs 31 that are fixed to and project outwardly from the side rails 32 of the conveyor frame, ride in vertical guideways 33 on the adjacent side sections of the main frame.

The frame 22, in addition to the side rails 32, has cross members 34 which connect the opposite ends of the rails, and two pairs of intermediate cross members 35.

The bed or platen 23 is preferably a casting and has a flat top wall 36 with parallel downwardly projecting side flanges 37 at'its opposite side edges which are parallel to the edges of the conveyor belt, and transverse flanges 38 at its opposite ends. There are also transverse stiffening ribs 39 and 40 at the underside of the top wall, the former having their ends joined to the side flanges 37 and the latter extending from one to the other of the intermediate ribs 39.

The bed or platen 23 is mounted in the frame 22 by four levers 41 located between and pivoted to the rails 32 of the frame and the side flanges 37 of the bed. These levers are arranged in pairs, one pair at each end of the bed or platen, with the levers of each pair fixed to and connected by parallel cross shafts 42 and 43. The shafts 42 which are shorter than the shafts 43, have their ends journalled in sealed anti-friction bearings 44 (FIG. 5) mounted in the sdie flanges 37 of the bed or platen and the ends of the longer shafts 43 are journalled in similar bearings 45 that are mounted in the side rails 32 of the frame 22. The frame, bed and levers thus constitute a parallelogram that can be collapsed and opened to provide a range of up and down motion for the bed or platen relative to the frame 22.

Two air springs 46 interposed between the bed or platen 23 and the frame 22, provide controllable resistance to descent of the bed or platen with respect to the frame. These air springs are simply rubber walled chambers such as those sold by the Firestone Rubber Company under its trademark Firestone Airmount.- They are seated upon the intermediate cross members of the frame, each in line with and under one of the two sanding heads, and bear against the underside of the top wall 36 of the bed or platen. Both air springs are connected with a source of air pressure, as diagrammatically shown in FIG. 7, so that in the absence of downward pressure on the bed or platen, it will be lifted to its maximum elevation. That position is determined by the length of four cap screws 47 that are threaded into lugs 48 at the side edges of the top wall 36 of the bed or platen, and slidably pass through holes in plates 49 fixed to the underside of the cross members 35 of the frame 22. Abutment of the heads of these screws with the underside of the plates 49 limits upward movement of the bed or platen with respect to the frame 22.

As shown in FIG. 7, the air springs may have either high or low-pressure therein, depending upon the setting of a selector valve 50. In its low pressure position, the selector valve connects the air springs with the pressure source through an adjustable pressure regulator 51 which is set to deliver air at a predetermined low pressure; while in its other position, the valve connects a second pressure regulator 52 between the pressure source and the air springs. The regulator 52 is adjusted at the factory to render the bed or platen rigid and unyielding up to the capacity of the machine, but to allow it to yield in the event of an overload. Accordingly, the regulator 52 is preferably so located on the machine as to be relatively inaccessible, while the other low pressure regulator 51 is placed where it can be readily adjusted by the operator.

The machine is thus quickly and easily adjustable to maintain any selected feed force between the work and the abrasive belt. Finish sanding will therefore be possible under ideal conditions, no matter what the size and nature of the work, for with the pressure regulator 51 properly adjusted and the selector valve 50 correctly set, upon entry of the work into the machine the bed or platen will float up or down as needed to maintain just the right amount of feed force; and, of course, as it floats it will retain its exactly horizontal orientation.

When lumber or other workpieces are to be dimensioned, the operator simply sets the selector valve to'its high pressure position, whereupon the bed or platen becomes rigid and, within the capacity of the machine, non-yielding. Such rigidity is of course necessary if accurate dimensioning is to be had.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purpose of illustration. Thus, for instance, although the invention has been described as embodied in a sanding machine having but two sanding heads, it is obvious that it applies equally well to single-head and multiple-head sanding machines; and also to machines in which the sanding head or heads are below the conveyor assembly.

The invention is defined by the following claims:

1. In a wide belt sanding machine having a main frame, a conveyor assembly mounted in the main frame and including a power driven endless'conveyor belt having a substantially horizontal work engaging stretch for feeding work through the machine, and a sanding head including a powder driven endless abrasive belt and backup means opposite said stretch of the conveyor belt and supporting the abrasive belt against the thrust of the work fed through the machine, the improvement by which work can be held against the thus supported abrasive belt with either a high force that does not yield up to the capacity of the machine for abrasive dimensioning of work or a low force for finish sanding, and which improvement comprises:

A. a rigid conveyor frame for the conveyor assembly having the endless conveyor belt mounted thereon with its work engaging stretch substantially horizontal;

B. platen means having a flat surface across which said stretch of the conveyor belt slides and by which it is pressed towards the backup means to hold work against the abrasive belt, said platen means having sides that are parallel with the edges of the conveyor belt;

C. movable mounting means connecting the platen means with the rigid conveyor frame for movement of the platen means relative to said rigid frame, towards and from the backup means, said mounting means at all times restraining the platen means against tilting from a position at which its said flat surface is substantially horizontal;

D. regulatable force producing means reacting between the platen means and the rigid conveyor frame to urge the platen means towards the backup means; and

E. controllable force regulating means operatively connected with said force producing means and by which the force applied thereby may be adjusted to be high or low.

2. In a wide belt sanding machine, the improvement set forth in claim 1,

wherein said movable mounting means along with the platen means and the rigid conveyor frame forms a parallelogram linkage.

3. The wide belt sanding machine of claim 1, wherein said movable mounting means comprises paired rigidly connected levers, one of each pair thereof being between one of the side rails of the rigid conveyor frame and the adjacent side of the platen means, and

bearing means connecting said levers at the ends thereof to the side rails of the rigid conveyor frame and to the platen means, so that the levers rock during movement of the platen means relative to the rigid conveyor frame.

4. The wide belt sanding machine of claim 1, wherein the rigid conveyor frame is rectangular and is mounted in the main frame of the machine for up and down translatory motion,

and wherein jack screws at the corners of the rigid conveyor frame support the same and provide for adjustment of the elevation of the entire conveyor assembly.

5. The wide belt sanding machine of claim 1, wherein said force producing means comprises air spring means connected with a source of air pressure,

and wherein said force regulating means comprises adjustable pressure regulator means connected between said air spring means and the source of air pressure.

6. The wide belt sanding machine of claim 5, wherein there are two pressure regulators, one adjusted to supply high pressure to the air spring means and the other adjusted to supply low pressure to the air spring means,

and valve means for alternatively connecting one or the other of said pressure regulators between the pressure source and the air spring means. 

1. In a wide belt sanding machine having a main frame, a conveyor assembly mounted in the main frame and including a power driven endless conveyor belt having a substantially horizontal work engaging stretch for feeding work through the machine, and a sanding head including a powder driven endless abrasive belt and backup means opposite said stretch of the conveyor belt and supporting the abrasive belt against the thrust of the work fed through the machine, the improvement by which work can be held against the thus supported abrasive belt with either a high force that does not yield up to the capacity of the machine for abrasive dimensioning of work or a low force for finish sanding, and which improvement comprises: A. a rigid conveyor frame for the conveyor assembly having the endless conveyor belt mounted thereon with its work engaging stretch substantially horizontal; B. platen means having a flat surface across which said stretch of the conveyor belt slides and by which it is pressed towards the backup means to hold work against the abrasive belt, said platen means having sides that are parallel with the edges of the conveyor belt; C. movable mounting means connecting the platen means with the rigid conveyor frame for movement of the platen means relative to said rigid frame, towards and from the backup means, said mounting means at all times restraining the platen means against tilting from a position at which its said flat surface is substantially horizontal; D. regulatable force producing means reacting between the platen means and the rigid conveyor frame to urge the platen means towards the backup means; and E. controllable force regulating means operatively connected with said force producing means and by which the force applied thereby may be adjusted to be high or low.
 2. In a wide belt sanding machine, the improvement set forth in claim 1, wherein said movable mounting means along with the platen means and the rigid conveyor frame forms a parallelogram linkage.
 3. The wide belt sanding machine of claim 1, wherein said movable mounting means comprises paired rigidly connected levers, one of each pair thereof being between one of the side rails of the rigid conveyor frame and the adjacent side of the platen means, and bearing means connecting said levers at the ends thereof to the side rails of the rigid conveyor frame and to the platen means, so that the levers rock during movement of the platen means relative to the rigid conveyor frame.
 4. The wide belt sanding machine of claim 1, wherein the rigid conveyor frame is rectangular and is mounted in the main frame of the machine for up and down translatory motion, and wherein jack screws at the corners of the rigid conveyor frame support the same and provide for adjustment of the elevation of the entire conveyor assembly.
 5. The wide belt sanding machine of claim 1, wherein said force producing means comprises air spring means connected with a source of air pressure, and wherein said force regulating means comprises adjustable pressure regulator means connected between said air spring means and the source of air pressure.
 6. The wide belt sanding machine of claim 5, wherein there are two pressure regulators, one adjusted to supply high pressure to the air spring means and the other adjusted to supply low pressure to the air spring means, and valve means for alternatively connecting one or the other of said pressure regulators between the pressure source and the air spring means. 